The present invention relates to an integrated spatial sensor and transducer, and in particular to a housing combining a transducer and spatial sensor.
Ultrasound has become a popular technique for the imaging and measuring of internal organs and anatomy. Ultrasound has several advantages over MRI and CT scanning: ultrasound is real-time, non-invasive, non-radiative, and relatively less expensive to buy and maintain compared to MRI and CT equipment. As with most medical technology, ultrasound systems are evolving to take advantage of new technologies and in response to the ever-increasing demands of medical professionals. One of the most requested features on ultrasound systems is the ability to present an image having the appearance of 3-D. Such an image is produced from a 3-D matrix of data. Generally, three dimensional data is presented in one of two forms: a surface scanned structure or a volume scanned structure. Either structure is formed by isonifying a volume and rendering the data to produce a 2-D image showing a 3-D object (referred to herein as a 3-D image).
Currently, there are two different methods for obtaining scan data in preparation for rendering a 3-D surface. The first method involves the use of a 1-D transducer which typically uses a linear array of elements to produce a 1-D slice of data. Alternatively, a single element transducer can be mechanically oscillated. After each slice is obtained, the sonographer (or more generically xe2x80x9cuserxe2x80x9d) moves the transducer to obtain another slice. Software is then used to stitch together a volume data set.
The second method involves the use of a two-dimensional transducer array to isonify a volume. In this method, two broad categories exist. Some systems use a so-called 1.5-D array, which comprises several rows of elements. A 1.5-D array can be conceptually thought of as a stack of convention 1-D arrays, each independently steerable along the azimuth. A 1.5-D array is not steerable in the elevation direction. A true 2-D array is a matrix of elements (and is sometimes referred to as a xe2x80x9cmatrix arrayxe2x80x9d) which acts as a unified whole and is steerable in the elevation direction. True 2-D array transducers are believed to be capable of producing a three dimensional volume of data without requiring significant operator involvement. At the present time, true 2-D transducers are largely experimental and very expensive, but the results have exceeded expectations. However, it has been determined that the response of tissue structures perpendicular to the face of the 2-D array is attenuated, such that some of the image produced by echoes off of such tissue structures is faint or nonexistent.
For the present, the first method of obtaining a plurality of data slices and stitching them together to form a volume data set is the preferred method of obtaining a 3-D image.
Freehand imaging is a method to develop 3-D images in which the sonographer moves a 1-D array across a patient xe2x80x9cfreehandxe2x80x9d and a specialized graphic processor attempts to warp together a 3-D image. One innovation that has greatly improved the image quality of 3-D images produced using the freehand method is the use location sensors externally mounted on a 1-D ultrasound transducer to register the spatial location and orientation with respect to translation and angulation of acquired ultrasound images. This method is typically referred to as the calibrated freehand method. To develop 3-D images, each 2-D image pixel is mapped to a physical location in the patient""s coordinate set. Data sets obtained from the scan are transformed into a Cartesian coordinate system to enable visualization similar to that provided by CTs or MRIs. Typically, a graphics workstation, such as those offered by SILICON GRAPHICS, assists with real-time visualization. Further, animation can be employed to perform rotations and zooming or to create a xe2x80x9ccine-loopxe2x80x9d display. Using such techniques, reconstructed 3-D images of the heart, blood vessels, stomach and other organs can be developed. Essentially, the 2-D image slices or xe2x80x9cplanesxe2x80x9d that stand-alone ultrasound provides are xe2x80x9cpastedxe2x80x9d together to provide a 3-D data set which can be rendered and displayed on a 2-D monitor. The 3-D data set is amenable to interaction and manipulation, and can be shared for remote consults via download or stored digitally.
Ascension Technology Corporation produces several models of magnetic location sensors under their FLOCK OF BIRDS(trademark) line that are suitable for use with the calibrated freehand method. For example, the DC-pulsed magnetically tracked mini-sensor (18 mmxc3x978 mmxc3x978 mm) of the miniBIRD(trademark) system measures 6 degrees of freedom when mounted on an ultrasound probe and are suitable for internal or external anatomical explorations. The pcBIRD(trademark) is a 6 degree of freedom tracker on a PC card that dedicates a separate processor for each receiver. It measures the location and orientation of a small receiver referenced to a magnetic transmitter. The electronics board plugs into the ISA slot of any PC computer.
FIG. 1 is a block diagram of a known ultrasound imaging system 100 configured for freehand scanning. An ultrasound unit 110 generally comprises a housing (such as a cart) supporting an imaging unit that includes transmission and reception circuits (including for example a beamformer) along with an image processing unit including display circuits. A transducer 112, connected to the ultrasound unit 110, outputs and receives ultrasound signals under the control of the imaging unit so as to scan a patient 114 in a known manner.
The ultrasound imaging system 100 is configured for use with the miniBIRD system from ASCENSION TECHNOLOGY CORPORATION. Like all known freehand imaging systems, Ascension Technologies"" applications call for the external attachment of a sensor to a transducer. A transmitter 116 is positioned in the vicinity of the patient 114, typically in connection with a bed or table upon which the patient 114 rests. A receiver 118, affixed to the surface of the transducer 112, receives a pulsed DC magnetic field transmitted by the transmitter 116. From measured magnetic field characteristics, the receiver 118 computes its location and orientation and makes this information available to a host computer 120 via a controller 122. The controller 122 synchronizes operation of the transmitter 116 and receiver 112 under the direction of the host computer 120.
The host computer 120 is also in communication with the ultrasound unit 110. The host computer 120, using location information from the receiver 118 and ultrasound image data from the ultrasound unit 110, tags individual frames of ultrasound image data with location information and xe2x80x9cstitchesxe2x80x9d together the various frames, using known algorithms, to produce 3-D images. For example, EchoTech 3-D Imaging Systems Inc. of Lafayette, Colo. produces systems that are capable of interfacing with the miniBIRD system and various ultrasound systems to produce real-time (or more accurately near real-time) 3-D images.
Systems similar to the one shown in FIG. 1 have several drawbacks. The first, and perhaps the most dangerous, is that such systems require a number of separate devices and a plurality of cables to connect the devices. For example, the transducer 112 has two cables extending therefrom, one going to the controller 122 and one going to the ultrasound unit 110. Additionally, the controller 122, transmitter 116 and host computer 120 all have various cables extending therefrom. In the already crowded medical environment, such clutter can lead to disaster, torn cables, shattered equipment, and perhaps even injury to the patient or attending professionals. A second problem arises due to the external attachment of the receiver 118, that of indeterminate calibration. Each time the receiver 118 is re-attached to the transducer 112 , a calibration procedure should be initiated to determine the orientation between the transducer 112 and receiver 118. This orientation information is critical for accurate xe2x80x9cstitchingxe2x80x9d in the host computer 120. As critical as this information is, there may be times when operators fail to perform such calibration, due to time constraints. Additionally, the method used to attach the receiver 118, i.e. velcro, glue, or straps, all have the potential to shift during use, causing artifacts in the stitched output.
The present inventors have recognized a need for a more accurate and user friendly calibrated freehand device. The present inventors have also invented new models of use for transducers (either 1-D or 2-D ) equipped with location sensing devices.
An ultrasound system comprising an ultrasound unit and a transducer. The transducer including a transducer housing integrating at least one element and a first spatial locator unit. The ultrasound unit includes an imaging unit that receives an echo signal from the at least one element of the transducer and outputs echo data. A second spatial locator unit, in communication with the first spatial locator unit, is integrated with the ultrasound unit. The second spatial locator unit in connection with the first spatial locator unit enables the determination of a location of the transducer housing.
The novel ultrasound system is particularly useful in producing 3-D images with 1-D arrays and improving the imaging quality of 3-D images by simplifying set-up, calibration and use of the ultrasound system. For example, the novel ultrasound system facilitates a method comprising the steps of isonifying a first volume from a first position, using a 2-D array of elements, in a first scanning operation; determining a relative location of the first position; receiving first echo data from the first scanning operation and relating the relative location of the first position to the first echo data; isonifying a second volume from a second position, using a 2-D array of elements, in a second scanning operation, the second volume overlapping at least a portion of the first volume; determining a relative location of the second position; receiving second echo data from the second scanning operation and relating the relative location of the second position to the second echo data; and creating a display of the at least a portion of the first volume using the first echo data and the second echo data.
As another example, the novel ultrasound system facilitates the automatic powering down of a transducer or system based on a location of a second spatial locator fixed relative to the ultrasound unit. Because the location of the second spatial locator is fixed, the location of the transducer relative to the ultrasound unit can easily be determined such that when the transducer is left lying around or returned to the ultrasound unit, power can automatically be shut off to the system or transducer. Of course the system could also be placed in a sleep mode based o n the location of the transducer.